Description
Synonymy - Mus coypus Molina 1782; Myopotomus bonairensis Geoffroy-St.-Hillaire 1805; Myocastor coypus bonairensis Thomas 1919
Other Taxonomic Grouping - The subspecies most likely introduced to Chesapeake Bay and North America was M. c. bonairensis (Kinler et al. 1987).
Potentially Misidentified Species- Muskrat
Taxonomy
| Kingdom | Phylum | Class | Order | Family | Genus |
|---|---|---|---|---|---|
| Animalia | Chordata | Mammalia | Rodentia | Myocastoridae | Myocastor |
Synonyms
Invasion History
Chesapeake Bay Status
| First Record | Population | Range | Introduction | Residency | Source Region | Native Region | Vectors |
|---|---|---|---|---|---|---|---|
| 1943 | Established | Expanding | Introduced | Regular Resident | South America | South America | Fisheries(Fisheries Accidental) |
History of Spread
Myocastor coypus (Nutria) is native to South America. The subspecies M. c. bonariensis, native to Argentina, Uruguay, Paraguay, and southern Brazil, is the form which has been widely introduced (Gosling and Baker 1990). Myocastor coypus was first imported into CA in 1899 in an attempt to establish a fur farm. During the 1930's, several attempts were made to start Nutria fur farms in various parts of the United States but these failed due to poor reproductive success and low fur prices. In 1937, E. A. McIlhenny imported 13 M. coypus to Avery Island LA in order to start a fur farm. He released some 21 aninals in 1940, and others in later years. Many other animals probably escaped from other fur farms in the area (Bernard 2002). Myocastor coypus spread through AL, GA, MS, TX, and FL in the 1940's and 50's, assisted by frequent local escapes from fur farms. Some deliberate releases were made for the control of aquatic vegetation (Kinler et al. 1987; McCann et al. 1996). By 1983-84, feral M. coypus were established in 15 states, with major population centers around Chesapeake Bay, southeast VA-northeast NC, the Gulf Coast from FL to TX, and western OR-WA, 'In the United States, all significant M. coypus populations are in coastal habitats' (Kinler et al. 1987).
Myocastor coypus have been widely introduced around the world, with established populations in England (Gosling and Baker 1990) and elsewhere in Europe, Russia, the Middle East, Africa and Japan (Kinler et al.1987).
Myocastor coypus were first brought into MD at the Fur Animal Field Station at Blackwater National Wildlife Refuge, Dorchester County in 1939, where they were kept for experimental purposes. Some animals were kept in outdoor enclosures in the marshes. In the spring of 1943, 5 escaped M. coypus were killed in a nearby boathouse. Several landowners in the vicinity also released M. coypus. In 1956, an eradication program was begun on the refuge, and in 1960-61 a heavy freeze killed many animals (Paradiso 1969; Willner et al. 1979). By 1969, Paradiso considered that 'the Nutria in Maryland marshes are only precariously established.'
However, in the late 60's and 70's M. coypus populations increased again, despite a population crash due to severe weather in 1976-77. By 1979, they were established along the Eastern Shore from Eastern Neck (Kent County) south to to the VA border, with smaller populations on the Western Shore along the Potomac River and Patuxent River (Willner et al. 1979). In VA, they were reported as abundant around Back Bay, just south of the Chesapeake Bay mouth (Wass 1972). According to Reshetiloff (1994), 'Around the Chesapeake, M. coypus are found mainly on the lower Eastern Shore counties of Maryland, but have been found in Patuxent and Potomac Rivers in the past'. In 1994, the M. coypus population was estimated at 100,000 animals (Anonymous 1994). An eradication program has been under study for M. coypus populations on the Eastern Shore of Chesapeake Bay (Anonymous 1994). Trapping began in January 2002, and eradication in the Blackwater National Wildlife Refuge was expected to take 3 years (Bounds and Mollett 2000). Nutria were eradicated from Blackwater National Wildlife Refuge by November of 2004 (Fahrenthold 2004), and eradication efforts have continued on the Eastern Shore. By July 2009, 12,000 nutira had been killed. As numbers of the nutria decrease, locating the survivors becomes more difficult. Use of radio-tagged animals is being considered to locate the remaing survivors. Access to private property has been a problem, but most landowners have cooperated. (Cooper 2009; Mike Haramis, Stephen Kendrot, personal communications; Frears 2011). As the population decreases, detection became more diffiuclt. Hair snares were found to be more successful than remote camers for detection (Pepper et al. 2016).
History References - Anonymous 1994;Bernard 2002; Bounds and Mollett 2000; Gosling and Baker 1990; Kinler et al.1987; McCann et al. 1996; Paradiso 1969; Reshetiloff 1994; Wass 1972; Willner et al. 1979
Invasion Comments
Ecology
Environmental Tolerances
| For Survival | For Reproduction | |||
|---|---|---|---|---|
| Minimum | Maximum | Minimum | Maximum | |
| Temperature (ºC) | -10.0 | 35.0 | ||
| Salinity (‰) | 0.0 | 0.0 | ||
| Oxygen | ||||
| pH | ||||
| Salinity Range | fresh-poly |
Age and Growth
| Male | Female | |
|---|---|---|
| Minimum Adult Size (mm) | 400.0 | 420.0 |
| Typical Adult Size (mm) | 550.0 | 525.0 |
| Maximum Adult Size (mm) | 635.0 | 600.0 |
| Maximum Longevity (yrs) | 6.0 | 6.0 |
| Typical Longevity (yrs | 4.0 | 4.0 |
Reproduction
| Start | Peak | End | |
|---|---|---|---|
| Reproductive Season | |||
| Typical Number of Young Per Reproductive Event |
|||
| Sexuality Mode(s) | |||
| Mode(s) of Asexual Reproduction |
|||
| Fertilization Type(s) | |||
| More than One Reproduction Event per Year |
|||
| Reproductive Startegy | |||
| Egg/Seed Form |
Impacts
Economic Impacts in Chesapeake Bay
Myocastor coypus (Nutria) were introduced to Chesapeake Bay as fur animals, but there has been little demand for their fur. Consequently, this species has provided a very small benefit, while adversely affecting marsh habitats, waterfowl, and a more desirable furbearer, Ondatra zibethicus (Muskrat).
Fisheries - 'Only recently have Maryland trappers begun to harvest substantial numbers of Myocastor coypus. This is becuse Maryland trappers previously had equipment specifically to harvest muskrats and not the much large Nutria. As Myocastor coypus populations in Maryland increased, more and more trappers purchased larger traps with which to harvest Myocastor coypus' (Willner et al. 1979). However, frequent heavy mortalities due to severe winter weather may limit the trappers' investment (Willner et al. 1979). As of 1994, 'At present there is almost no commercial fur market and only a very small meat market. This situation, combined with M. coypus' reproductive success, has led to a boom in their population' (Reshetiloff 1994). In 1986-87, the total value of M. coypus pelts from MD wetlands was $822 (Tiner and Burke 1995).
Costs to Fisheries- Myocastor coypus have been responisble for extensive habitat change, conversion of marsh to bare mud or open water, affecting fish and waterfowl habitat and feeding and nursery areas (Kinler et al. 1987; Willner et al. 1979). They may compete for food with O. zibethicus. This competion is considered insignificant in brackish marshes in MD (Willner et al. 1979), but may be more important in fresh and tidal fresh marshes where their plant preferences may overlap more (Kinler et al. 1987). Myocastor coypus also evict O. zibethicus from their lodges during winter, possibly affecting the native rodents' survival in severe weather (Reshetiloff 1994). They damage weirs protecting impounded marshes on wildlife refuges, through burrowing.
A control program relying heavily on bounties was proposed by the MD Department of Natural Resources, and initally scheduled to begin in 1994, at an estimated cost of 2.3 million dollars. However, advice from L. M. Gosling indicated that bounty hunting might be ineffective. The estimated cost of the revised program was 4 million dollars, resulting in postponement 'for up to two years' (Anonymous 1994). A 3-year pilot M. coypus management program has been proposed (Bounds and Mollett 2000), including marking and tracking of animals, continued experimental assessment of grazing, and capture of M. coypus by professional trappers. This program began in 2003, eliminated nutria from Blackwater National Wildlife Refuge by November 2004, and continues through 2009 (Fahrenthold 2002; Cooper 2009, Mike Haramis, Stephen Kendrot, personal communications 2009 )
Agriculture- Myocastor coypus do sometimes eat corn in fields adjacent to their habitats (Willner et al. 1979).
Boating - Myocastor coypus may cause damage to river banks, dikes, levees, through burrowing (Gosling and Baker 1990).
Habitat Change - See 'Ecological Impacts'. Damage to marshes, levees, and river banks may also affect nearby houses and other property (Gosling and Baker 1990).
References - Anonymous 1994; Gosling and Baker 1990; Kinler et al. 1987; Reshetiloff 1994; Tiner and Burke 1995; U.S. Fish and Service 2001; Willner et al. 1979.
Economic Impacts Outside of Chesapeake Bay
Myocastor coypus (Nutria) were originally imported widely as fur animals, and in some countries deliberately released in order to start feral populations. However, the quality of their pelt was not highly regarded, and in the United States and elsewhere, many M. coypus farms failed in the 1940's due to lack of demand (Kinler et al. 1987), probably resulting in many deliberate and accidental releases. Some deliberate releases were made in FL and elsewhere for control of aquatic vegetation in canals, but these populations were soon regarded as nuisances, damaging crops and desirable vegetation (McCann et al. 1996).
The harvest of M. coypus pelts in LA amounted to 1.3 million pelts per year for 1977-84, ~6 million dollars, and about 53% of LA's fur production (Kinler et al. 1987). Kinler et al. (1987) considered that at the time of writing, the harvest in LA was sufficient to offset most of the economic damage in many areas, but that changes in market demand could reduce the harvest, increasing agricultural and habitat damage.
Myocastor coypus may damage crops in fields near their habitats, including corn (Wilner et al. 1979), cabbage, lettuce, peas (McCann et al. 1996) and sugar-cane (Kinler et al. 1987).
In Britain, M. coypus ('Coypu') is regarded as an unmitigated nuisance because of damage to dikes, riverbanks, levees, agricultural crops, and wildlife habitat, and was subject to an eradication program. About 34,000 animals were trapped in east Anglia, and by 1989, the species was believed to have been eradicated from Britain (Gosling and Baker 1990). Negative impacts have been noted also in the Netherlands, Germany, Russia, and Turkey (Lever 1985).
References - Gosling and Baker 1990; Kinler et al. 1987; Lever 1985; McCann et al. 1996; Wilner et al. 1979.
Ecological Impacts on Chesapeake Native Species
Myocastor coypus (Nutria) have reached high densities on the Eastern Shore of Maryland, and are regarded as a serious threat to the native biota of tidal marshes, and to the function of the marsh ecosystem
Competition- Myocastor coypus with Ondatra zibethicus (Muskrats) for food, but the two rodents have different food preferences in brackish MD marshes. Myocastor coypus prefers Schoenoplectus americanus (=Scirpus olneyi, Three-Square Rush), 80% of its diet, while O. zibethicus' preferred food is Typha angustifolia (Narrow-Leafed Cattail). Schoenoplectus americanus is only about 17% of O. zibethicus' diet (Willner et al. 1979). In some areas (e.g. OR, TX), with different plant community composition, more definite feeding competition between O. zibethicus and M. coypus has been noted (Willner et al. 1979; Kinler et al. 1987). An additional form of interference is that M. coypus invades and evicts O. zibethicus from their lodges in winter (Reshlitoff 1994), which could affect the latter's survival.
Herbivory - Grazing by M. coypus appears to have had significant effects on plant abundance and species composition in much of its introduced range. On the lower Eastern Shore of the Chesapeake Bay, Willner et al. (1979) noted bare areas formerly covered with Schoenoplectus americanus. Exclosure experiments show that exclusion of M. coypus permits revegetation of these areas (Haramis and Colona 1998).
Similar impacts have been observed in other parts of M. coypus' introduced range. In fresh and oligohaline marshes of the Pearl River LA, total above-ground plant biomass was reduced by 30% in plots exposed to M. coypus grazing compared with exclosures, but species richness was not affected (Taylor et al. 1995). This is surprising given M. coypus' strong food preferences, but Taylor et al. (1995) explained the apparent lack of selection by wasteful feeding. In other areas, favored plant species, such as Schoenoplectus sp. (bulrushes), Sagittaria latifolia (Broadleaf Arrowhead), and Spartina cynosuroides (Big Cordgrass) were replaced by less favored plants (Kinler et al. 1987). In Britain, Typha spp. (Cattails) were largely replaced by Phragmites australis (Common Reed), and some other favored plants [Rumex hydrolapathum (Water Dock); Cicuta virosa(Cowbane)] were all but eliminated (Gosling and Baker 1990).
Habitat Change- Myocastor coypus' most significant impact may be converting large areas of marsh into bare mud or open water called 'eat-outs' through grazing. 'We noted broad areas of bare mud in many Dorchester County marsh areas formerly covered with three-square rush' (Willner et al. 1979). In Blackwater National Wildlife Refuge (Dorchester County MD), 6 square miles (1553 hectares) has been converted from marsh to open water, and 53% of the remaining marsh has been damaged (Haramis and Colona 1998). Effects of M. coypus' herbivory have been especially dramatic in LA where the animal's effect on marshes is combined with seawater intrusion due to wells, sea-level rise, and land subsidence (Kinler et al. 1987).
References - Gosling and Baker 1990; Haramis and Colona 1998; Kinler et al. 1987; Reshlitoff 1994; Taylor et al. 1995; Willner et al. 1979.
Ecological Impacts on Other Chesapeake Non-Native Species
Myocastor coypus (Nutria) have reached high densities on the Eastern Shore of Maryland, and are regarded as a serious threat to the native biota of tidal marshes, and to the function of the marsh ecosystem
Herbivory - Phragmites australis (Common Reed), probably mostly the introduced genotype) is grazed by M. coypus in brackish MD marshes. It is less preferred than Three-Square Rush (Schoenoplectus americanus) but formed 0-33% of the diet (~6% annual average) (Willner et al. 1979). In England, M. coypus grazing has decreased the area of reed-swamps (Gosling and Baker 1990), but in the eastern United States grazing by M. coypus, Ondatra zibethicus (Muskrat), and other herbivores was considered inadequate for biological control of invasive Phragmites australis (Common Reed) populations (Marks et al. 1994). Myocastor coypus also may graze on the introduced Typha angustifolia (Narrow-leaved Cattail), which occasionally is an important food, comprising up to 12% of the diet (Willner et al. 1979).
References - Gosling and Baker 1990; Marks et al. 1994; Willner et al. 1979
References
Anonymous (1994) Nutria eradication program put on hold in Maryland, Bay Journal 4: 10Bounds, D. L.; Mollett, T. A. (2000) Can Nutria be eradicated in Maryland?, In: Salmon, T. P.; Crabb, A. C.(Eds.) Proceedings of the 19th Vertebrate Pest Conference. , . Pp. 121-126
Chabreck, Robert H.; Love, John R.; Linscombe, Greg (1981) Food and feeding habits of nutria in brackish marsh in Louisiana, In: Chapman, Joseph A. and Pursley, Duane(Eds.) World Furbearer Conference Proceedings. , Frostburg, Maryland. Pp. 531-543
Cooper, Dick (6/2008) Effort close to exterminating nutria on Delmarva Peninsula: Rodents blamed, in part, for loss of 8,000 acres of marsh at Blackwater Refuge, Bay Journal None: None
Doncaster, C. Patrick; Dumonteil, Eric; Barré, Hervé; Jouventin, Pierre (1990) Temperature regulation of young coypus (Myocastor coypus) in air and water., American Journal of Physiology 257: R1220-1227
Nov. 17, 2004 Maryland battles the nutria.. Washington Post
Frears, Darryl (10/28/2011) In Maryland, a renewed effort to eradicate swamp rats from the DelMarva Peninsula, Washington Post None: None
Gosling, L. M., Baker, S. J. (1981) Coypu (Myocastor coypus) potential longevity, Journal of Zoology (London) 197: 285-312
Gosling, L. M.; Baker, S. J. (1990) Family Myocastoridae., In: Corbett, Gordon G., and Harris, Stephen.(Eds.) The Handbook of British Mammals.. , Oxford. Pp. 267-278
Hall, E. Raymond; Kelson, Keith R. (1959) The Mammals of North America, , New York. Pp.
1998 The effect of Nutria (<i>Myocastor coypus</i>) on marsh loss in the Eastern Shore. http://www.pwrc.usgs.gov/resshow/nutria.htm
Kinler, Noel W.; Linscombe. Greg, Ramsey; Paul R. (1987) Nutria., In: Novak, M., Baker; J. A., Obard, M.(Eds.) Furbearer Management and Conservation in North America.. , Toronto. Pp. 326-344
Lever, Christopher (1985) Naturalized mammals of the world., In: (Eds.) . , London. Pp.
Marks, Marianne; Lapin, Beth; Randall, John (1994) Phragmites australis (P. communis): Threats, management, and monitoring, Natural Areas Journal 14: 285-294
Paradiso, John L. (1969) Mammals of Maryland, , Washington, D.C.. Pp.
Reshetiloff, Kathryn (1994) 'Nutria or muskrat, you make the call', Bay Journal 4: 20, 12
Shirley, Mark G.; Chabreck, Robert; Linscombe, Greg (1981) Foods of nutria in fresh marshes of southeastern Louisiana., In: Chapman, Joseph A.; Pursely, Duane(Eds.) World Furbearer Conference Proceedings. , Frostburg MD. Pp. 517-530
Taylor, Katherine L.; Grace, James B. (1995) The effects of vertebrate herbivory on plant community structure in the coastal marshes of the Pearl River, Louisiana, USA, Wetlands 15: 68-73
Tiner, Ralph W., Jr.; Burke, David G. (1995) Wetlands of Maryland, , Newton Corner, MA. Pp.
Walker, Ernest P. (1968) Mammals of the World, , Baltimore, MD. Pp.
Wass, Melvin L. (1972) A checklist of the biota of lower Chesapeake Bay, Special Scientific Report, Virginia Institute of Marine Science 65: 1-290
Willner, G. R.; Dixon, K. R.; Chapman, J. A. (1983) Age determination and mortality of the nutria (myocastor coypus) in maryland, u.s.a., Zeitschrift fur Saugetierkunde 48: 19-34
Willner, Gale R.; Chapman, Joseph A.; Pursley, Duane (1979) Reproduction, physiological responses, food habits, and abundance of nutria on Maryland marshes., Wildlife Monographs 65: 1-43
Wilsey, Brian J.; Chabreck, Robert H.; Linscombe, R. Greg (1991) Variation in nutria diets in selected freshwater forested wetlands of Lousiana, Wetlands 11: 63-278